This invention relates to jigsaws and in particular to powered jigsaws which impart an orbital movement to the blade. That is to say, those which advance the blade slightly in the direction of feed during a cutting stroke. Such saws are also referred to as pendulum jigsaws when the advancement of the blade is through a pendulum action.
It is desirable in such jigsaws to provide the possibility of adjustment of the pendulum action because blade advancement is not always an advantage when cutting certain materials. One preferred arrangement is described in U.S. Pat. No. 4,238,884-Walton. In this arrangement, the roller supporting the back of the jigsaw blade is mounted on a bell crank lever. The other end of the lever is acted on by a pin passing through a shaft. In the region of the pin, the bell crank lever is provided with a circular cam profile which lies in the plane of rotation of the shaft and which is centered on the axis of the shaft. The other end of the pin is acted upon by a similar cam profile of a fork lever pivoted about an axis parallel to the shaft. The other end of the fork lever is forked and is journalled about an eccentric circular cam surface formed on a gear driven by the jigsaw motor. The same cam surface also moves a counterweight to balance the up and down movement of the jigsaw blade and carrier therefor.
The jigsaw blade and carrier are reciprocated by the gear. Thus as the motor rotates and the jigsaw carrier and blade are reciprocated, the fork lever is also reciprocated and through its cam surface, the pin and the bell crank lever, the blade is given a reciprocating movement in the feed direction of the saw, as well as its normal reciprocating cutting stroke along its axis.
The adjustment of the pendulum action is effected by rotation of the shaft so as to alter the points of application of the fork on the pin between maximum and minimum positions.
In U.S. Pat. No. 4,238,884, the shaft simply extends out of the rear of the housing of the saw and is provided with a knob for manual adjustment. However, because of the need to provide room between the motor housing and the sole plate of the saw in which to accommodate that knob, the saw appears somewhat "top-heavy" and unbalanced. Moreover, it is desirable to provide the saw with vacuum suction means in the region of the knob so that dust created during sawing can be removed and collected. It is therefore, an object of this invention to provide a jigsaw having the advantages and features of that disclosed in U.S. Pat. No. 4,238,884 but which does not suffer the aforementioned disadvantages.